通过给定枚举的所有枚举变体迭代

发布于 2025-02-04 06:35:52 字数 190 浏览 1 评论 0原文

是否有可能迭代给定枚举的所有枚举变体。我有一个std :: unordered_map＆lt; enum，value_type＆gt;，enum variant作为键。我需要检查给定枚举的所有枚举变体是否存在为std :: unordered_map＆lt; enum，value_type＆gt;中的键。

原文

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

旧时模样 2025-02-11 06:35:53

考虑制作诸如allkeypresent的助手方法，在下面的示例程序中说明

#include <iostream>
#include <unordered_map>
//declare an enum
enum DIR : int {NORTH, SOUTH, WEST, EAST}; 

/**
 * AllKeysPresent: return true if and only if map contains all enum keys
 */
template<typename T = int> 
bool AllKeysPresent(const std::unordered_map<DIR, T>& myMap)
{
    bool allKeysPresent = true;
    //loop over enum, starting with the first entry up and including the last entry
    for (int key = DIR::NORTH; key <= DIR::EAST; key++)
    {
        if (myMap.find(static_cast<DIR>(key)) == myMap.end())
        {
            allKeysPresent = false;
            break;
        }
    }
    //TODO: check if at least one valid key is present. return false if the map is empty
    return allKeysPresent;
}

int main()
{
    //make a map with all keys
    std::unordered_map<DIR, int> mapWithAllKeys = { {DIR::NORTH, -1}, {DIR::SOUTH, -2}, {DIR::WEST, -3}, {DIR::EAST, -4} };
    std::unordered_map<DIR, int> mapWithSomeKeys = { {DIR::NORTH, -1}, {DIR::SOUTH, -2} };
    std::cout << AllKeysPresent(mapWithAllKeys) << std::endl;
    std::cout << AllKeysPresent(mapWithSomeKeys) << std::endl;
    return 0;
}

了
enum dir：int {dir_first，北，南，西，东，dir_last};
其中dir_first和dir_last只是虚拟条目，然后将循环迭代更改为for（int key = dir :: dir :: dir_first+1; key＆lt; dir：dir：dir_last; key ++）。这样，如果某人决定在您的枚举中添加新条目，例如southwest，那么allkeyspresent仍然可以正常工作

Consider making a helper method like AllKeyPresent illustrated in a sample program below

#include <iostream>
#include <unordered_map>
//declare an enum
enum DIR : int {NORTH, SOUTH, WEST, EAST}; 

/**
 * AllKeysPresent: return true if and only if map contains all enum keys
 */
template<typename T = int> 
bool AllKeysPresent(const std::unordered_map<DIR, T>& myMap)
{
    bool allKeysPresent = true;
    //loop over enum, starting with the first entry up and including the last entry
    for (int key = DIR::NORTH; key <= DIR::EAST; key++)
    {
        if (myMap.find(static_cast<DIR>(key)) == myMap.end())
        {
            allKeysPresent = false;
            break;
        }
    }
    //TODO: check if at least one valid key is present. return false if the map is empty
    return allKeysPresent;
}

int main()
{
    //make a map with all keys
    std::unordered_map<DIR, int> mapWithAllKeys = { {DIR::NORTH, -1}, {DIR::SOUTH, -2}, {DIR::WEST, -3}, {DIR::EAST, -4} };
    std::unordered_map<DIR, int> mapWithSomeKeys = { {DIR::NORTH, -1}, {DIR::SOUTH, -2} };
    std::cout << AllKeysPresent(mapWithAllKeys) << std::endl;
    std::cout << AllKeysPresent(mapWithSomeKeys) << std::endl;
    return 0;
}

I would also recommend declaring your enum like this
enum DIR : int {DIR_FIRST, NORTH, SOUTH, WEST, EAST, DIR_LAST};
where DIR_FIRST and DIR_LAST are just dummy entries, and change for loop iteration to for (int key = DIR::DIR_FIRST + 1; key < DIR:DIR_LAST; key++). This way, if someone decides to add a new entry to your enum like SOUTHWEST, then AllKeysPresent will still work

回复收藏 0 原文

~没有更多了~